In recent years there has been an increasing demand in industry and defense for polymeric substances which would either remain intact or continue to serve in a more or less degraded state under conditions where temperatures far above the ordinary are encountered. In many cases highly cross-linked organic polymers have been found promising. The phthalocyanine structure is one of the most thermally stable organic structures known. Attractive properties like resistance to chemical attack, electrical properties, catalytic activity and moderate cost of manufacture with good coloring properties have made phthalocyanines the object of intensive world-wide investigations. Many attempts to synthesize polymers based on phthalocyanines have failed to provide the expected thermal stability. Phthalocyanine polymers so far produced have shown less thermal stability than the phthalocyanine monomer itself because of the presence of impurities, weak chemical bonds and low degree of polymerization with structural inhomogeneity. Impurities have the considerable effect of decreasing thermal stability of the phthalocyanine monomers as well as the polymers produced from them. It is well known that the way in which the repeating units are linked is reflected in the properties of the polymers. If the repeating phthalocyanine mer units are linked in the way phenyl groups are linked in biphenyl, the conjugation extends throughout the macromolecule thereby increasing the extent of delocalization of the .pi.-electrons. This is expected to increase the conductivity as well as the thermal stability of the phthalocyanine polymers.